Novel Inter-ocular and Inter-hemisphere Asymmetry Analysis of Macular Inner Retinal Layers for Glaucoma Diagnosis: Swept-source Optical Coherence Tomography Wide View Study

Abstract

 

Purpose

 

To report a novel asymmetry analysis of macular inner retinal layers using swept-source optical coherence tomography (OCT)

 

Methods

 

Three-dimensional scans of 12 mm width were acquired from both normal and glaucoma subjects by swept-source deep-range imaging OCT (DRI OCT-1 Atlantis). The thickness of the retinal nerve fiber layer (RNFL), ganglion cell-inner plexiform layer (GCIPL), ganglion cell complex (GCC), and total retina were calculated within a 6×6 mm macular area divided into a 30×30 grid of 200×200 μm squares. For each of the corresponding cells, the thickness differences between the included and contra-lateral eyes and between the upper and lower macula halves were determined. All of the negative values, representing relative decreases compared with the corresponding cells, were selected for the analysis. The negative differences were displayed on a gray-scale asymmetry map. Black cells were defined as thickness decreases over the relevant cut-off values. The cut-off value for black cells in the RNFL, GCIPL, and GCC analyses was 20 μm, and for the total retina analysis, 30 μm.

 

Results

 

In this study, 20 eyes of 20 normal subjects and 20 eyes of 20 glaucoma patients were included. The average negative inter-ocular and inter-hemisphere differences of GCIPL were -2.59±0.93 μm and -3.52±0.89 μm in the normal group and -4.53±1.03 μm and -6.18±1.44 μm in the glaucoma group (Table). The overall extent of the four layers’ thickness decrease was larger in the glaucoma group than in the normal group (all Ps < 0.05). The numbers of black cells on the inter-ocular and inter-hemisphere asymmetry maps of GCIPL were 7.4±10.6 and 21.6±21.3 in the normal group and 46.3±26.3 and 97.0±50.6 in the glaucoma group (Table). The numbers of black cells on all of the asymmetry maps were larger in the glaucoma group than in the normal group (all Ps < 0.05).

 

Conclusions

 

The novel asymmetry analysis of macular inner retinal layers using swept-source OCT showed significant differences between the normal and glaucoma patients’ groups. These findings suggest that novel asymmetry analysis can be complementary to other tests for differentiating glaucoma patients from normal subjects.  

 

 

Figure. (top left) RNFL photograph, (top right) GCIPL thickness map, (bottom left) Inter-ocular asymmetry map, (bottom right) Inter-hemisphere asymmetry map